Melting and freezing temperatures of confined Bi nanoparticles over a wide size range

2017 ◽  
Vol 50 (6) ◽  
pp. 1590-1600 ◽  
Author(s):  
Hermann Franz Degenhardt ◽  
Guinther Kellermann ◽  
Aldo Felix Craievich
Keyword(s):  
Structural Model ◽  
Sodium Borate ◽  
Experimental Procedure ◽  
X Ray ◽  
X Ray Scattering ◽  
Wide Range ◽  
Freezing Temperatures ◽  
Bi Nanoparticles ◽  
Ray Scattering

The size dependences of the melting and freezing temperatures,TmandTf, respectively, of spherical Bi nanoparticles embedded in a sodium borate glass were determined by applying a new experimental procedure based on the combined and simultaneous use of small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS). This experimental procedure is particularly useful for materials in which a widely polydisperse set of nanoparticles are embedded. The results provide additional and stronger evidence supporting the main previous conclusions: (i) the melting and freezing temperatures both decrease linearly for increasing reciprocal radius (1/R); and (ii) the effect of undercooling is suppressed for Bi nanoparticles with radii smaller than a critical value equal to 1.8 nm. These results confirm a previously proposed low-resolution structural model for Bi nanocrystals below their melting temperature and with radiusR> 1.8 nm, which consists of a crystalline core surrounded by a disordered shell. In the present work, a number of samples with different and partially overlapping radius distributions were studied, allowing the determination ofTm(R) andTf(R) functions over a wide range of radii (1 <R< 11 nm). Comparison of the experimentally determinedTm(R) andTf(R) functions corresponding to different samples indicates good reproducibility of the experimental results. This allowed the verification of the robustness of the experimental procedure based onin situcombined use of SAXS and WAXS for determination of the radius dependence of the melting and freezing temperatures of spherical nanoparticles in dilute solution.

X-ray scattering from coals

1954 ◽  
Vol 226 (1165) ◽  
pp. 143-169 ◽  
Keyword(s):  
Structural Model ◽  
Fourier Transforms ◽  
Chemical Properties ◽  
Bedding Plane ◽  
Optical Data ◽  
X Ray ◽  
X Ray Scattering ◽  
Wide Range ◽  
Liquid Type ◽  
Ray Scattering

This paper describes the results of X-ray scattering experiments on a series of vitrain-coals of varying rank. The scattering at high angles is interpreted in terms of condensed aromatic layers; the diameters of the layers are determined and are found to increase with increasing rank; the percentage carbon in the form of layers is also estimated. Fourier transforms calculated for the scattering at lower angles show that the layers occur partly singly, and partly in groups of two, three or more stacked parallel to each other. The degree of local parallel stacking increases with increasing rank. There is a preferred orientation of the layers parallel to the bedding plane, which becomes more marked the higher the rank of the coal. The diffraction peak at ~20 Å, found for coals with 85 to 94% C, is considered to be a consequence of ‘liquid-type’ packing of the most frequently occurring groups containing two to three layers. The diameters of the layers determined from the transforms (~8 Å) are in good agreement with the results of intensity calculations, and the values obtained from the scattering at high angles. The scattering at very small angles is measured with a two-crystal spectrometer for spacings up to ~5000 Å. The scattering is related to porosity; the scattering curves do not support the existence of a close-packed arrangement of ‘micelles’ of fairly constant diameter less than ~5000 Å, but suggest that there are anisotropic cracks and pores of a wide range of sizes, some of which must exceed ~5000 Å. The total scattering indicates the existence of disk cracks preferentially orientated parallel to the bedding plane. In terms of a proposed structural model, coalification is a process of condensation, ordering of the layers, and flattening of the structure. A ‘liquid-type’ structure is formed, which is most perfect at ~89% C and accounts for the minimum of porosity. Anthracitization is probably accompanied by a clustering of the layers, which results in a rapid increase of layer diameter, in irregular packing, and in an increase of porosity. The properties of the proposed structure model of coal are discussed and compared with the known physical and chemical properties of coal, e. g. density, optical data, porosity and mechanical properties, and some of the problems still outstanding are indicated.

scholarly journals Synthesis and Advanced Characterization of Polymer-Protein Core-Shell Nanoparticles

Catalysts ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 730
Author(s):  
Erik Sarnello ◽  
Tao Li
Keyword(s):  
Particle Size ◽  
Small Angle ◽  
Core Shell ◽  
Assembly Process ◽  
Shell Nanoparticles ◽  
X Ray ◽  
X Ray Scattering ◽  
Wide Range ◽  
Core Shell Nanoparticles ◽  
Ray Scattering

Enzyme immobilization techniques are widely researched due to their wide range of applications. Polymer–protein core–shell nanoparticles (CSNPs) have emerged as a promising technique for enzyme/protein immobilization via a self-assembly process. Based on the desired application, different sizes and distribution of the polymer–protein CSNPs may be required. This work systematically studies the assembly process of poly(4-vinyl pyridine) and bovine serum albumin CSNPs. Average particle size was controlled by varying the concentrations of each reagent. Particle size and size distributions were monitored by dynamic light scattering, ultra-small-angle X-ray scattering, small-angle X-ray scattering and transmission electron microscopy. Results showed a wide range of CSNPs could be assembled ranging from an average radius as small as 52.3 nm, to particles above 1 µm by adjusting reagent concentrations. In situ X-ray scattering techniques monitored particle assembly as a function of time showing the initial particle growth followed by a decrease in particle size as they reach equilibrium. The results outline a general strategy that can be applied to other CSNP systems to better control particle size and distribution for various applications.

scholarly journals Towards a methodology for the characterisation of the fabric of wet clays using X-ray scattering

2019 ◽  
Vol 92 ◽  
pp. 01005
Author(s):  
Georgios Birmpilis ◽  
Reza Ahmadi-Naghadeh ◽  
Jelke Dijkstra
Keyword(s):  
Materials Science ◽  
Measurement Techniques ◽  
Invasive Technique ◽  
Colloidal Systems ◽  
Characteristic Distance ◽  
X Ray ◽  
Hydrophobic Coating ◽  
X Ray Scattering ◽  
Wide Range ◽  
Ray Scattering

X-ray scattering is a promising non-invasive technique to study evolving nano- and micromechanics in clays. This study discusses the experimental considerations and a successful method to enable X-ray scattering to study clay samples at two extreme stages of consolidation. It is shown that the proposed sample environment comprising flat capillaries with a hydrophobic coating can be used for a wide range of voids ratios ranging from a clay suspension to consolidated clay samples, that are cut from larger specimens of reconstituted or natural clay. The initial X-ray scattering results using a laboratory instrument indicate that valuable information on, in principal evolving, clay fabric can be measured. Features such as characteristic distance between structural units and particle orientations are obtained for a slurry and a consolidated sample of kaolinite. Combined with other promising measurement techniques from Materials Science the proposed method will help advance the contemporary understanding on the behaviour of dense colloidal systems of clay, as it does not require detrimental sample preparation

scholarly journals Fast in-situ X-ray scattering reveals stress sensitivity of gypsum dehydration kinetics

2021 ◽  
Vol 2 (1) ◽  
Author(s):  
Christoph Eckart Schrank ◽  
Oliver Gaede ◽  
Tomasz Blach ◽  
Katherine Carmen Michelle Gioseffi ◽  
Stephen Mudie ◽  
...  
Keyword(s):  
Stress Sensitivity ◽  
Water Vapour Pressure ◽  
Fast Time ◽  
Dehydration Kinetics ◽  
Efficient Design ◽  
X Ray ◽  
Triggered Earthquakes ◽  
X Ray Scattering ◽  
Wide Range ◽  
Ray Scattering

AbstractThe dehydration of gypsum to hemihydrate has been studied for decades because it is an important model reaction for understanding fluid-triggered earthquakes, and due to the global use of plaster of Paris in the construction industry. The dehydration kinetics of gypsum strongly depend on temperature and water vapour pressure. Here, we perform fast, time-resolved synchrotron X-ray scattering on natural alabaster samples, finding that a small elastic load accelerates the dehydration reaction significantly. The mechanical acceleration of the reaction consumes about 10,000 times less energy than that due to heating. We propose that this thermodynamically surprising finding is caused by geometry-energy interactions in the microstructure, which facilitate nucleation and growth of the new crystalline phase. Our results open research avenues on the fundamental thermo-mechanics of crystal hydrates and the interaction of stress and chemical reactions in crystalline solids with a wide range of implications, from understanding dehydration-triggered earthquakes to the energy-efficient design of calcination processes.

A multi-length-scale USAXS/SAXS facility: 10–50 keV small-angle X-ray scattering instrument

2013 ◽  
Vol 46 (5) ◽  
pp. 1508-1512 ◽  
Author(s):  
Byron Freelon ◽  
Kamlesh Suthar ◽  
Jan Ilavsky
Keyword(s):  
Small Angle ◽  
Soft Matter ◽  
High Energy ◽  
X Rays ◽  
X Ray ◽  
X Ray Scattering ◽  
Wide Range ◽  
And Performance ◽  
New Facility ◽  
Ray Scattering

Coupling small-angle X-ray scattering (SAXS) and ultra-small-angle X-ray scattering (USAXS) provides a powerful system of techniques for determining the structural organization of nanostructured materials that exhibit a wide range of characteristic length scales. A new facility that combines high-energy (HE) SAXS and USAXS has been developed at the Advanced Photon Source (APS). The application of X-rays across a range of energies, from 10 to 50 keV, offers opportunities to probe structural behavior at the nano- and microscale. An X-ray setup that can characterize both soft matter or hard matter and high-Zsamples in the solid or solution forms is described. Recent upgrades to the Sector 15ID beamline allow an extension of the X-ray energy range and improved beam intensity. The function and performance of the dedicated USAXS/HE-SAXS ChemMatCARS-APS facility is described.

scholarly journals Size and Concentration Determination of Colloidal Nanocrystals by Small-Angle X-Ray Scattering

2018 ◽  
Author(s):  
Jorick Maes ◽  
Nicolo Castro ◽  
Kim De Nolf ◽  
Willem Walravens ◽  
Benjamin Abécassis ◽  
...  
Keyword(s):  
Band Gap ◽  
Small Angle ◽  
Accurate Determination ◽  
Band Gap Energy ◽  
Colloidal Nanocrystals ◽  
X Ray ◽  
Absolute Scale ◽  
X Ray Scattering ◽  
Ray Scattering

<div> <div> <div> <p>The accurate determination of the dimensions of a nano-object is paramount to the de- velopment of nanoscience and technology. Here, we provide procedures for sizing quasi- spherical colloidal nanocrystals (NCs) by means of small-angle x-ray scattering (SAXS). Using PbS NCs as a model system, the protocols outline the extraction of the net NC SAXS pattern by background correction and address the calibration of scattered x-ray intensity to an absolute scale. Different data analysis methods are compared, and we show that they yield nearly identical estimates of the NC diameter in the case of a NC ensemble with a monodisperse and monomodal size distribution. Extending the analysis to PbSe, CdSe </p> </div> </div> <div> <div> <p>and CdS NCs, we provide SAXS calibrated sizing curves, which relate the NC diameter and the NC band-gap energy as determined using absorbance spectroscopy. In compari- son with sizing curves calibrated by means of transmission electron microscopy (TEM), we systematically find that SAXS calibration assigns a larger diameter than TEM calibration to NCs with a given band gap. We attribute this difference to the difficulty of accurately sizing small objects in TEM images. To close, we demonstrate that NC concentrations can be directly extracted from SAXS patterns normalized to an absolute scale, and we show that SAXS-based concentrations agree with concentration estimates based on absorption spectroscopy.</p></div></div></div>

Diffuse x-ray scattering from InGaAs/GaAs quantum dots

2003 ◽  
Vol 799 ◽  
Author(s):  
Rolf Köhler ◽  
Daniil Grigoriev ◽  
Michael Hanke ◽  
Martin Schmidbauer ◽  
Peter Schäfer ◽  
...  
Keyword(s):  
Quantum Dots ◽  
Synchrotron Radiation ◽  
Diffuse Scattering ◽  
Data Evaluation ◽  
X Ray ◽  
X Ray Scattering ◽  
Gaas Matrix ◽  
Wetting Layers ◽  
Ray Scattering

ABSTRACTMulti-fold stacks of In0.6Ga0.4As quantum dots embedded into a GaAs matrix were investigated by means of x-ray diffuse scattering. The measurements were done with synchrotron radiation using different diffraction geometries. Data evaluation was based on comparison with simulated distributions of x-ray diffuse scattering. For the samples under consideration ((001) surface) there is no difference in dot extension along [110] and [-110] and no directional ordering. The measurements easily allow the determination of the average indium amount in the wetting layers. Data evaluation by simulation of x-ray diffuse scattering gives an increase of Incontent from the dot bottom to the dot top.

Sign in / Sign up

Export Citation Format

Share Document